声明类变量问题

Question

What do these var declarations actually do inside of a PHP class:

class VbForumsPageMain extends BxDolPageView {
    var $_oMain;
    var $_oTemplate;
    var $_oConfig;
    var $_oDb;

    function VbForumsPageMain(&$oMain) {
        $this->_oMain = &$oMain;
        $this->_oTemplate = $oMain->_oTemplate;
        $this->_oConfig = $oMain->_oConfig;
        $this->_oDb = $oMain->_oDb;
        parent::BxDolPageView('vb_forums_main');
    }
}

Are they neccessary and do they add any extra use to the variables? I'm not sure whey they're in the class twice.

Answer 1

The first use is defining them, the second is initialising them. It's good practice to define them up front and even better practice to set the appropriate visibility .

Have a read of the PHP documentation for more information - what you learn now will put you in good stead for the future.

Answer 2

This has been answered here, hope it helps - What does PHP keyword 'var' do? .

It basically declares public properties or the class, but you should use private , public and protected instead.

Answer 3

Yes, they are needed as they define the extension of the class. The VbForumsPageMain class has the same properties (variables) as the BxDolPageView extended by those vars . The function below sets the values and the structure of the class.

Answer 4

Just to add to other answers: These definitions at the beginning of the class are very important to auto-competition in IDEs. If you don't define the properties at the beginning, the IDE might give you "undefined property" errors. Furthermore it gives you a quick overview of which properties are available in a class.